New Line Cinema/Metro-Goldwyn-Mayer Pictures/Warner Bros. Pictures(LONDON) -- Sir Ian McKellan, who can be seen in theaters starting on Dec. 14 reprising his Lord of the Rings role as Gandalf in The Hobbit: An Unexpected Journey, has revealed he's been battling prostate cancer.

The acclaimed actor, best known for his roles in the X-Men and Lord of the Rings films, revealed he's had the disease for "six or seven years," according to The Sun, but explained, "I am examined regularly and it's contained."

The 73-year-old actor says of his diagnosis, "It's like when you go for an HIV test -- you go 'Argh, is this the end of the road?' You monitor it and you have to be careful it doesn’t spread."

McKellan explains his doctors decided against any aggressive treatment for now.